Yes. The important thing is that you always have to consider the catchment area. As far as I know, you don't have a lot of connecting trains in urban rail transit hubs. If you want to improve the overall journey times, you have to consider the first and last mile. People have to go to the city station, then leave the city station for somewhere else—a final destination. You always have to optimize overall journey times, so you need a transport or mobility model for the overall system.
If you want to become competitive against the car in terms of convenience and all of that stuff, you at least need very competitive travel times. This means they can't take much more time than a car would.
That's it.